Clinical Efficacy Of Ginkgo Biloba In Cognitive Impairment, Dementia & Alzheimer’s Disease 
Author: David Puchol Esparza 

Introduction

Ginkgo Biloba (traceable back 300 million years) is the oldest surviving species of tree. It has been cultivated extensively for both ceremonial and medical purposes, and some particularly revered trees have been lovingly tended for over 1,000 years. The Ginkgo tree has been used in Traditional Chinese Medicine for over 4,000 years.The German Commission E ‘approves’ Ginkgo Biloba extracts for effective therapy in cases of memory deficits,depression,impaired concentration,dizziness, tinnitus or migraine. The most well-established herbal treatment for Alzheimer's disease and,indeed, one of the few herbs that probably deserves the description "proven effective", is the ancient herb Ginkgo Biloba (Bratman et al.,2000).

In numerous research studies involving geriatric patients,remarkable success has been demonstrated using Ginkgo Biloba Extract (GBE) to treat cerebral insufficiency. A recent meta-analysis,published in the British Journal of Pharmacology, analyzed the quality of research conducted in over 40 clinical studies investigating Ginkgo Biloba extract in the treatment of cerebral insufficiency. Cerebral insufficiency is a key factor associated with age-related mental decline or dementia (including Alzheimer’s Disease). The resulting analysis concluded that the reviewed research was on par with research conducted on traditional psychoactive medications for treatment of dementia and that Ginkgo Biloba extract is effective in reducing all symptoms of cerebral insufficiency, including impaired mental function and memory loss.

This psychoactive herb is gaining recognition as a ‘brain tonic’ that enhances memory because of its positive effects on the vascular system, especially in the cerebellum.Four mechanisms of action are thought to account for some of the positive and therapeutic effects that have been described :

1. A cognition-enhancing action (e.g.memory and neurotransmitter support).
   
2. A stress-alleviating action (e.g.antioxidant effects and prevention of brain damage).
   
3. A gene-regulatory action (e.g.general neuroprotective effects).
   
4. A vaso-regulatory action (e.g.systemic and brain circulation).

Ginkgo Biloba is made up of ginkgo flavone glycosides, several terpene molecules unique to Ginkgo Biloba (ginkgolides and bilobalide) and organic acids.The therapeutic benefits of GBE rely primarily on two groups of active components : the ginkgo flavone glycosides and the terpene lactones.

A.-The 24% ginkgo flavone glycoside designation on GBE labels indicates the carefully measured balance of bioflavonoids. These bioflavonoids are primarily responsible for Ginkgo’s antioxidant activity and may mildly inhibit platelet aggregation.

B.-The unique terpene lactone components found in GBE (known as ginkgolides and bilobalide) typically make up 6% of the extract.They are associated with increased circulation to the brain and other parts of the body as well as exert a protective action on nerve cells.

Today,Ginkgo Biloba is the most widely prescribed herb in Germany, reaching a total prescription count of over 6 million in 1995 (Schulz et al.,1998). German physicians consider it to be as effective as any drug treatment for Alzheimer’s Disease and other severe forms of memory and mental function decline (Kleijnen & Knipschild,1992).

Dosage Recommendations

The standard dosage of Ginkgo Biloba is 40 to 80 mg 3 times daily of a 50 : 1 extract standardized to contain 24% ginkgo-flavone glycosides. Levels of toxic ginkgolic acid and related alkylphenol constituents should be kept under 5 parts per million (Bratman et al.,2000).

Most clinical trials have used between 120–240 mg of GBE,standardized to contain 6% terpene lactones and 24% flavone glycosides per day, generally divided into two or three portions. Relatively high amounts (240 mg per day) have been used in reports studying people with age-associated memory loss,mildcognitive impairment,resistant depression and mild-to-moderate Alzheimer’s Disease (Blumenthal et al.,1997).

Interactions & Side Effects

According to recent studies on drug and herb interactions,GBE should not be used while taking blood thinning medications such as warfarin, heparin coumarin or derivative. Caution should also be taken with aspirin as ‘anecdotes’ have been recorded of unfavorable interactions (Bergner,1997).

Possible interactions (Bratman et al.,2000)....

1. Antidepressant drugs,especially SSRI : Ginkgo might remedy sexual side effects.
   
2. Antipsychotics : Ginkgo might help them work better with fewer side effects.
   
3. Natural substances with blood-thinning properties,such as high-dose vitamin E.

Side effects are rare with use of the standardized extract. Ginkgo Biloba extract is, very rarely, associated with allergic skin reactions and migraines. Mild gastrointestinal upset occurs in less than 1 % of patients in clinical trials. Some patients with poor blood flow to the brain (cerebrovascular insufficiency) may experience a mild, transient headache for the first one or two days of use.The current German Commission E monograph lists no contraindications to the use of GBE during pregnancy or lactation (Blumenthal et al.,2000).

In all the clinical trials of GBE up through 1991 combined, involving a total of almost 10,000 participants, the incidence of side effects produced by GBE was extremely small.There were 21 cases of gastrointestinal discomfort, and even fewer cases of headaches, dizziness and allergic skin reactions (DeFeudis,1991).

Clinical Applications of Ginkgo Biloba Extract : Scientific Evidences

01.-Several clinical studies have been conducted to evaluate the efficacy of Ginkgo Biloba Extracts (GBE) in preventing the progression of Alzheimer type of dementia.The hallmark of this neurodegenerative disease is the formation of amyloid b deposits in certain regions of the brain. The importance of this accumulation for the onset and progression of Alzheimer’s Disease is compelling. It has been shown that cytotoxic action of amyloid b on neurons results from free radical damage to susceptible cells and antioxidant activity of Ginkgo Biloba extracts may be responsible for a possible protective effect in Alzheimer’s Disease (Hofferberth,1994).

02.-According to a 1992 article published in Lancet, over 40 double-blind controlled trials have evaluated the benefits of GBE in treating age-related mental decline.Of these, eight were rated of good quality, involving a total of about 1,000 people and producing positive results in all but one study.The authors of the Lancet article felt that the evidence was strong enough to conclude that GBE is an effective treatment for this disease. Clinical studies since 1992 have verified this conclusion, both in people with Alzheimer's Disease and those without the disorder (Kleijnen & Knipschild,1992).

03.-A more recent study published in ‘Pharmacopsychiatry’ evaluated the overall efficacy of the Ginkgo Biloba special extract -EGb 761- in outpatients suffering from mild to moderate primary degenerative dementia of the Alzheimer type or multi-infarct dementia.216 individuals with Alzheimer's Disease or Dementia due to small blood clots were given either of Ginkgo Biloba Extract or placebo. After 24 weeks there was a significant improvement in the Ginkgo Biloba group compared with control group (Kanowski et al.,1996).

04.-JAMA -Journal of the American Medical Association- (1997) published qualitative research showing that GBE appears to slow Alzheimer's Disease. The randomly assigned, double-blind, placebo-controlled study was performed for one year by neurologist Dr. Pierre L.LeBars and a team of scientists at the New York Institute for Medical Research. The study found that 27 percent of patients who took 120 mg of GBE for six months or longer improved their mental functioning, including memory, reasoning, and the ability to learn, compared to only 14 percent of those taking placebo. The study began with 309 patients -aged 45 or older- with most suffering from Alzheimer's Disease but also some with Dementia caused by strokes. The study showed that GBE can stabilize or even improve mental performance in one-third of those who are mildly impaired by Alzheimer's.According to Le Bars et al.(1997) "The mechanism of action of Ginkgo is only partially understood,although the main effects seem to be related to its antioxidative properties, involving compound families in the herb, including flavonoids, terpenoids (ginkgolides, bilobalide), and organic acids.”

05.-Mauer et al. (1997) recently completed a clinical study of the efficacy of GBE.They conducted a double-blind, randomized, placebo-controlled, parallel group design on twenty patients for three months. He used 240 mg/day of GBE-Egb 761 (Tebonin Forte) on twenty patients for three months. No adverse events were reported during the study. He concludes that "Efficacy of Ginkgo Biloba Special Extract -Egb 761- in mild to moderate dementia of Alzheimer's Type has been confirmed."

Conclusion

There are currently nearly 18 million people with Dementia in the world. This is set to rise to around 34 million by 2025. Of this total, 71 per cent will be living in developing countries. Although Alzheimer's Disease is not a ‘normal’ part of aging, the risk of developing this illness rises with age. Current research from the National Institute on Aging indicates that the prevalence of Alzheimer's Disease doubles every five years beyond age 65, and that nearly half of those over 85 have symptoms of the disease.

A massive body of scientific evidence supports a variety of medicinal uses of Ginkgo Biloba. In fact, the european medical community has recognized GBE as an effective compound in the treatment of cerebral insufficiency resulting in vascular dementia. Recent studies in which GBE demonstrated therapeutic effects in the treatment of dementia have even earned Ginkgo Biloba the approval of the German BGA for use in the treatment of Dementia,as well as memory deficits,impaired concentration, dizziness, tinnitus,headache (particularly when these are due to cerebral insufficiency) and depression.

Ginkgo Biloba Extract (GBE) could be an important herbal contribution to the treatment and prevention of Alzheimer's Disease. Ongoing scientific research continues to investigate the specific mechanisms by which Ginkgo Biloba provides health benefits. Ginkgo has been shown to be nutritional support for mental alertness, enhanced,blood vessel health, vitality level and circulatory health. Its high antioxidant activity is valuable for fighting age related conditions.With over 1,000 published research studies to date,Ginkgo Biloba is one of the best known, well-documented herbal medicine available today.

References

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About the author:
Article written by David Puchol Esparza
Psychologist and Naturopath

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